Experimental results of bulk acoustic wave transverse graded electrode patterns

This paper will present experimental results of various transverse graded electrode (TGE) patterns for bulk acoustic wave (BAW) resonators. The theory for the TGE BAW based on a stacked matrix theory has been previously introduced. By changing the electrode pattern structure, it is possible to predict and control the transverse mode shapes, and to some extent, the number and relative coupling to the various modes. Previous authors have presented single ring structures, which have shown some effects on the transverse modes. Based on theoretical predictions, several different types of BAW devices having an approximate center frequency of 10 MHz were designed, fabricated and tested. Electrode structures include various solid, single-ring and multi-ring electrode patterns. The various structures have different coupling to the higher order transverse modes and different equivalent circuit parameters and Q. Comparisons of predicted and measured device parameters which include impedance plots showing the effects of coupling, mode frequency separation, and equivalent electrical network parameters will be presented. A discussion of the measured results as related to the theoretical predictions will also be presented.